Devotion to Our Lady received a strong boost at the beginning of the 10th century with the monastic reform that gave shape to Mediæval Civilization.
After that epoch it became the general custom to dedicate Saturday to Our Lady. Saint Hugh the Great, ordered that in the abbeys and monasteries of his Order the Office should be sung and a Mass celebrated in honor of Mary Most Holy on Saturdays. A special Mass was composed in her honor for those occasions. To the regular Divine Office, Pope Urban Ⅱ added the Little Office of Our Lady to be sung on Saturdays.
There are many reasons why Saturday should be dedicated to the Most Holy Virgin. The best known grew from the particular devotion the medieval man had to the Resurrection of Our Lord Jesus Christ. The Gospels tell us that after the death of Our Lord, the Apostles, disciples and Holy Women did not believe in the Resurrection, even though Our Lord had predicted it various times.
Thus, from the hour that Our Lord died on the Cross on Good Friday until the Sunday of the Resurrection, only Our Lady believed in His Divinity and, therefore, only she had perfect faith. For, as Saint Paul says:
Without the resurrection our faith would be vain.
On that Saturday, therefore, on the whole earth only she personified the Catholic Church. For this reason mediæval man honored her especially on this day.